Fuel cell stack

ABSTRACT

A fuel cell stack is provided with a plurality of stacked separators. This fuel cell stack includes: terminals that extend from the separators; packing in which are formed a plurality of through holes through which the terminals are inserted; a packing casing that has a packing housing concave portion that envelops side surfaces of the packing and supports a bottom surface of the packing, and has through holes through which the terminals are inserted; and a connector housing that has a pressing surface that presses a top surface of the packing. Mountain-shaped protruding portions whose apex portions are formed by circumferential edges of apertures of the respective through holes are provided on the top surface of the packing, and the pressing surfaces of the connector housing are formed in a configuration that conforms to the side surfaces of the protruding portions. Internal surfaces of the through holes in the packing are in contact without a gap in between with external surfaces of the terminals. The sealing performance in extraction portions of terminals that are used for cell voltage detection is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priority,under 35 U.S.C. §121, to U.S. application Ser. No. 11/080,268, now U.S.Pat. No. 7,732,079, filed Mar. 14, 2005. This application also claimsthe benefit, under 35 U.S.C. §119, of foreign priority applicationsfiled in Japan: Serial No. 2004-076448, filed Mar. 17, 2004 and2004-200312, filed Jul. 7, 2004. The disclosures of the priorapplications are considered part of and are incorporated by reference inthe disclosure of this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel cell stack, and particularly toa waterproof structure that surrounds terminals used for voltagemeasurement in each cell.

Priority is claimed on Japanese Patent Application No. 2004-76448, filedMar. 17, 2004, and No. 2004-200312, filed Jul. 7, 2004, the contents ofwhich are incorporated herein by reference.

2. Description of Related Art

Among fuel cells that are mounted in a fuel cell vehicle or the like,there are those in which a solid polymer electrolyte membrane issandwiched between an anode electrode and a cathode electrode so as toform a membrane electrode structure. This membrane electrode structureis sandwiched between a pair of separators so as to form a cell (i.e., aunit fuel cell). In this type of fuel cell, typically, a plurality ofcells are stacked and used as a fuel cell stack.

In this fuel cell, if fuel gas (for example, hydrogen gas) is suppliedto the anode electrode and oxidizing gas (for example, air that containsoxygen) is supplied to the cathode electrode, then the hydrogen gas isionized at the anode electrode, and moves into the solid polymerelectrolyte membrane. Electrons then pass through an external load andmove into the cathode electrode, where they react with oxygen to createwater. Electrical energy can be extracted from this series ofelectrochemical reactions.

In this type of fuel cell, in order to determine whether or not eachcell is in a normal state when in operation, the voltage betweenseparators that constitute each cell (referred to below as the cellvoltage) is measured, and the power generating state of each cell iscontrolled.

As is described, for example, in Japanese Patent Application UnexaminedPublication No. 11-339828, a conventional technique is known forconnecting lead wires, which are connected to a cell voltage detectioncircuit, to the separators that employs a structure in which a socketshaped connector that is provided at a distal end of the lead wires isinserted into terminals formed in the separators.

In a fuel cell, in order to avoid short-circuiting between cells that iscaused by water entering from the outside, it is necessary forwaterproofing treatment to be performed around the terminals. However,providing an individual waterproofing member for each of the largenumber of terminals that is equal to the number of stacked separators isextremely complicated and gives rise to poor productivity.

Therefore, the present invention provides a fuel cell stack that enablesa terminal group made up of a plurality of terminals to be waterproofedall together without a waterproofing member needing to be providedindividually for each terminal, and that has a waterproofing mechanismwith excellent sealing properties.

SUMMARY OF THE INVENTION

In order to solve the above described problems, according to an aspectof the present invention, there is provided a fuel cell stack (forexample, the fuel cell stack 1 in the embodiments described below) thatis provided with a plurality of stacked separators (for example, theseparators 2 in the embodiments described below), comprising: terminals(for example, the terminals 3 in the embodiments described below) thatextend from an optional one of the separators; packing (for example, thepacking 20 in the embodiments described below) in which are formed aplurality of through holes (for example, the through holes 21 in theembodiments described below) through which the terminals are inserted; apacking casing (for example, the packing casing 11 in the embodimentsdescribed below) that has a packing housing concave portion (forexample, the packing housing concave portion 12 in the embodimentsdescribed below) that envelops side surfaces of the packing (forexample, the side surfaces 27 in the embodiments described below) andsupports a bottom surface (for example, the bottom surface 22 in theembodiments described below) of the packing, and has through holes (forexample, the through holes 13 in the embodiments described below)through which the terminals are inserted; and a connector member (forexample, the connector housing 30 in the embodiments described below)that has a pressing surface (for example, the internal surfaces 32 a ofthe tapered holes 32 in the embodiment described below) that presses atop surface (for example, the top surface 23 in the embodimentsdescribed below) of the packing, wherein internal surfaces of thethrough holes in the packing are in contact without a gap in betweenwith external surfaces of the terminals.

With this structure, the sealing performance between the through holesin the packing and the terminals is improved, and the terminals can bepositioned and placed in rows accurately.

Preferably, in the above described fuel cell stack, the internalsurfaces of the through holes in the packing are in contact without agap in between with the external surfaces of the terminals before thepacking is pressed.

With this structure, when the packing is pressed and compressed, theinternal surfaces of the through holes in the packing can be placed intight press contact with the external surfaces of the terminals.

Preferably, in the above described fuel cell stack, mountain-shapedprotruding portions (for example, the protruding portions 25 in theembodiment described below) whose apex portions (for example, the apexportions 25 a in the embodiment described below) are formed bycircumferential edges of apertures of the respective through holes areprovided on the top surface of the packing, and the pressing surfacesare formed in a configuration that conforms to the side surfaces (forexample, the side surfaces 25 b in the embodiment described below) ofthe protruding portions.

With this structure, the contact area (namely, the area of the sealportion) between the protruding portions of the packing and the pressingsurfaces of the connector member can be increased. In addition, becausethe side surfaces the protruding portions of the packing are compressedby a force exerted obliquely inwards from the pressing surfaces of theconnector member, the internal surfaces of the through holes in thepacking are in tighter press-contact with the external surfaces of theterminals.

Preferably, in the above described fuel cell stack, there is no ridgeline on the side surfaces of the protruding portions.

With this structure, the followingness of the protrusions in the packingrelative to the pressing surface when the packing is deformed by beingcompressed is excellent, and the sealing performance relative to thepressing surface can be further improved.

Preferably, in the above described fuel cell stack, each of the throughholes in the packing comprises a bottom portion through hole and a topportion through hole located above the bottom portion through hole inconformity with the terminal comprising a base portion covered by resinand a distal end portion located above the base portion and having anexposed metal surface, the top portion through hole having a horizontalcross section smaller than that of the bottom portion through hole.

Preferably, in the above described fuel cell stack, the packing isprovided with a lip seal that encloses through holes on a bottom surfaceof the packing.

According to another aspect of the present invention, there is provideda fuel cell stack (for example, the fuel cell stack 1 in the embodimentsdescribed below) that is provided with a plurality of stacked separators(for example, the separators 2 in the embodiments described below),comprising: terminals (for example, the terminals 3 in the embodimentsdescribed below) that extend from an optional one of the separators;packing (for example, the packing 20 in the embodiments described below)that has a plurality of through holes (for example, the through holes 21in the embodiments described below) through which the terminals areinserted, and that has an independent circumferential wall portion (forexample, the protrusions 28 in the embodiments described below) for eachthrough hole; a packing casing (for example, the packing casing 11 inthe embodiments described below) that has a packing housing concaveportion (for example, the packing housing concave portion 12 in theembodiments described below) that envelops the packing and supports abottom surface (for example, the bottom surface 22 in the embodimentdescribed below) of the packing, and has through holes (for example, thethrough holes 13 in the embodiment described below) through which theterminals are inserted; and a connector member (for example, theconnector housing 30 in the embodiment described below) that has apressing surface (for example, the tapered surfaces 37 a, the bulgeportions 37 b, and the flat surfaces 37 c in the embodiment describedbelow) that presses a top surface (for example, the protruding portions25 in the embodiment described below) and side surfaces (for example,the side surfaces 28 a in the embodiment described below) of therespective circumferential wall portions of the packing, wherein bulgeportions (for example, the bulge portions 29 and 37 b in the embodimentsdescribed below) are provided on at least one of the side surfaces ofthe circumferential wall portions and the pressing surfaces that pressthese side surfaces, and the bulge portions protrude towards so as to bein press contact with the other of the side surfaces of thecircumferential wall portions and the pressing surfaces, and internalsurfaces of the through holes in the packing are in contact without agap in between with external surfaces of the terminals.

With this structure, the sealing performance between the through holesin the packing and the terminals is improved, and the terminals can bepositioned and placed in rows accurately. In particular, in locationswhere the bulge portions have been provided, because it is possible toplace the internal surfaces of the through holes in the packing in closecontact with the external surfaces of the terminals, the sealingperformance is increased.

Preferably, in the above described fuel cell stack, the internalsurfaces of the through holes in the packing are in contact without agap in between with the external surfaces of the terminals before thepacking is pressed.

With this structure, when the packing is pressed and compressed, theinternal surfaces of the through holes in the packing can be placed intight press contact with the external surfaces of the terminals.

Preferably, in the above described fuel cell stack, mountain-shapedprotruding portions (for example, the protruding portions 25 in theembodiments described below) whose apex portions (for example, the apexportions 25 a in the embodiments described below) are formed bycircumferential edges of apertures of the respective through holes areprovided on the top surface of the circumferential wall portions of thepacking, and the pressing surfaces (for example, the tapered surfaces 37a in the embodiments described below) that press these top surfaces areformed in a configuration that conforms to the mountain-shapedconfiguration of the protruding portions.

With this structure, the contact area (namely, the area of the sealportion) between the protruding portions of the packing and the pressingsurfaces of the connector member can be increased. In addition, becausethe protruding portions of the packing are compressed by a force exertedobliquely inwards from the pressing surfaces of the connector member,the internal surfaces of the through holes in the packing are in tighterpress-contact with the external surfaces of the terminals.

Preferably, in the above described fuel cell stack, the circumferentialwall portions of the packing have no ridge line in a circumferentialdirection thereof.

With this structure, the followingness of the packing relative to thepressing surface when the packing is deformed by being compressed isexcellent, and the sealing performance relative to the pressing surfacecan be further improved.

Preferably, in the above described fuel cell stack, each of the throughholes in the packing comprises a bottom portion through hole at a lowerside of the circumferential wall portion of the packing and a topportion through hole at an upper side of the circumferential wallportion, and wherein the bulged portions are provided on the pressingsurfaces of the connector member such that an upper portion of thepressing surfaces presses the upper side of the circumferential wallportion and the bulged portions press the lower side of thecircumferential wall portion.

Preferably, in the above described fuel cell stack, the packing casingcomprises an O-ring that encircles the packing housing concave portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a connector unit of a firstembodiment of the fuel cell stack of the present invention.

FIG. 2 is an exploded perspective view of the connector unit of thisembodiment.

FIG. 3 is a perspective view of a packing casing used in this embodimentas seen from the bottom surface side.

FIG. 4 is an external perspective view of packing used in thisembodiment.

FIG. 5 is a perspective view of a connector housing used in thisembodiment as seen from the bottom surface side.

FIG. 6 is an enlarged cross-sectional view of the principal portionsshowing a state before the packing is compressed in the connector unitof this embodiment.

FIG. 7 is a cross-sectional view taken along the line A-A in FIG. 6.

FIG. 8 is an enlarged cross-sectional view of the principal portionsshowing a state after the packing has been compressed in the connectorunit of this embodiment.

FIG. 9 is a cross-sectional view taken along the line B-B in FIG. 8.

FIG. 10 is an external perspective view showing another example ofpacking.

FIG. 11 is an exploded perspective view of the connector unit of asecond embodiment.

FIG. 12 is an external perspective view of packing used in thisembodiment.

FIG. 13 is an enlarged cross-sectional view of the principal portionsshowing a state before the packing is compressed in the connector unitof this embodiment.

FIG. 14 is a cross-sectional view taken along the line C-C in FIG. 13.

FIG. 15 is an enlarged cross-sectional view of the principal portionsshowing a state after the packing has been compressed in the connectorunit of this embodiment.

FIG. 16 is a cross-sectional view taken along the line D-D in FIG. 15.

FIG. 17 is an enlarged cross-sectional view of the principal portionsshowing a state before the packing is compressed in the connector unitof yet another embodiment.

FIG. 18 is a cross-sectional view taken along the line E-E in FIG. 17.

FIG. 19 is an enlarged cross-sectional view of the principal portionsshowing a state after the packing has been compressed in the connectorunit of this embodiment.

FIG. 20 is a cross-sectional view taken along the line F-F in FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

The first embodiment of the fuel cell stack of the present inventionwill now be described with reference made to the drawings of FIGS. 1through 10.

As is shown in FIG. 1, a fuel cell stack 1 is formed by stacking aplurality of separators 2 that sandwich membrane electrode structures(not shown) inside a stack housing (not shown). The fuel cell stack 1 isalso provided with a connector unit that measures a voltage betweenadjacent separators 2 and 2.

As is shown in FIG. 2, the separators 2 are provided with plate-shapedterminals 3 that extend upwards from a top end portion of the separators2. In a state in which the separators 2 are stacked, the placementpositions of the terminals 3 are offset from each other in adjacentseparators 2 and 2. As a result, two columns of terminal groups 3A and3A are formed running in the stacking direction. Base portions 3 a ofthese terminals 3 are coated in resin, while metal surfaces of distalend portions 3 b thereof are exposed. The base portions 3 a are insertedthrough windows (not shown) in the stack housing, and the distal endportions 3 b protrude towards the connector unit 10.

The connector unit 10 is provided with a packing casing 11, two packings20 and 20, a connector housing 30, and a cover 40.

The packing casing 11 is a member that is installed on a top portion ofthe stack housing. Packing housing concave portions 12 that are formedin a narrow, elongated shape running in the stacking direction of theseparators 2 are provided in a relationship of 1 to 1 with each terminalgroup 3A on a top surface 11 a of the packing casing 11 in positionscorresponding to the terminal groups 3A and 3A.

FIG. 3 is a view showing an upside-down packing casing 11. Through holes13 that penetrate the packing housing concave portions 12 from a bottomsurface 11 b are provided in a relationship of 1 to 1 with each terminal3 at positions that correspond to the respective terminals 3 in thebottom surface 11 b of the packing casing 11. A bridge portion 14 isprovided between adjacent through holes 13 and 13 in the same terminalgroup 3A. Top surfaces of the bridge portions 14 (i.e., the surfacelocated on the bottom side in FIG. 3) are flush with a bottom surface 12a of the packing housing concave portions 12. The through holes 13 areformed at a size that enables a gap to be left when the terminals 3 areinserted therein, and the bottom side of the through holes 13 is formedas a tapered hole while the top side thereof is formed as a straighthole.

The packings 20 and 20 are formed from an elastic material, and they arecontained respectively in the packing housing concave portions 12 of thepacking casings 11. Examples of the elastic material used to form thepackings 20 include nitrile rubber (NBR), hydrogenated nitrile rubber(HNBR), fluoro rubber (FKM, FFKM), acrylic rubber (ACM), silicone rubber(VMQ, FVMQ), urethane rubber (AU, EU), ethylene propylene rubber (EPM,EPDM), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM),epichlorohydrin rubber (CO, ECO), isoprene rubber (IR), styrenebutadiene rubber (SBR), butadiene rubber (BR), novornene rubber (NOR),natural rubber, and other thermoplastic elastomers.

The planar configuration and planar dimensions of the packings 20 areset such that the packings 20 can be housed in the packing housingconcave portions 12 with substantially no gap between the two. Throughholes 21 through which the terminals 3 are inserted are formed in thepackings 20 extending from the bottom surface 22 to the top surface 23.These through holes 21 are provided in a relationship of 1 to 1 witheach terminal 3.

As is shown in FIGS. 6 to 9, a bottom side portion of each through hole21 is formed as a bottom portion through hole 21 a through which thebase portion 3 a, which is covered by resin, of the terminal 3 isinserted. The top side portion of each through hole 21 is formed as atop portion through hole 21 b through which the distal end portion 3 b,which has exposed metal surfaces, of the terminal 3 is inserted. Ahorizontal cross section of the top portion through hole 21 b is set soas to be smaller than that of the bottom portion through hole 21 a.Moreover, a horizontal cross section of the bottom portion through hole21 a is set so as to be slightly smaller than the horizontal crosssection of the base portion 3 a of a terminal 3. In addition, thehorizontal cross section of the top portion through hole 21 b is set soas to be slightly smaller than the horizontal cross section of thedistal end portion 3 b of a terminal 3. A bottom edge portion of thebottom portion through hole 21 a is formed as a tapered hole 21 c thatwidens as it approaches the bottom.

As is shown in FIG. 6 and FIG. 7, a lip seal portion 24 is formed in atoroidal shape by a single protruding bar so as to enclose all thethrough holes 21 on a bottom surface 22 of the packing 20.

As is shown in FIG. 4, a top surface 23 of the packing 20 is structuredsuch that a number of protruding portions 25 that are formed astruncated pyramids protrude from a flat portion 26. More specifically,the protruding portions 25 form quadrangular pyramid base shapes(namely, quadrangular pyramids with the top portion removed) that aremade up of a flat apex portion 25 a and four side surfaces 25 b that areconnected to the flat apex portion 25 a and gradually widen towards theends thereof. A top portion through hole 21 b is provided in the centerof each apex portion 25 a. As is shown in FIGS. 6 to 9, the boundarybetween each bottom portion through hole 21 a and top portion throughhole 21 b is positioned at substantially the same height as the flatportion 26. Note that when the packing 20 is contained inside thepacking housing concave portion 12, the packing housing concave portion12 envelops side surfaces 27 of the packing 20, and supports the bottomsurface 22 of the packing 20.

The connector housing 30 is placed on top of the packing casing 11, andapplies pressing force to the packings 20 so as to compress the packings20. The planar configuration and planar dimensions of the connectorhousing 30 are the same as those of the packing casing 11.

FIG. 5 is a view showing an upside-down connector housing 30. Narrowelongated protruding portions 31 and 31 are provided in parallel witheach other at positions corresponding to the respective terminal groups3A and 3A on the bottom surface 30 b of the connector housing 30. Theplanar configuration and planar dimensions of each protruding portion 31are set such that they can be inserted in the packing housing concaveportions 12 of the packing casing 11 so that substantially no gap isleft. Tapered holes 32, whose shape matches the side surfaces 25 b ofthe protruding portions 25 of the packing 20 and whose bottom surface 31a side is enlarged, are provided at positions corresponding to eachterminal 3 on the bottom surface 31 a of each protruding portion 31(i.e., on the upper surface as seen in FIG. 5). Straight holes 33continue from top portions of the tapered holes 32. Internal surfaces 32a of the tapered holes 32 form pressing surfaces that press the sidesurface 25 b of the protruding portions 25 of the packing 20. Thestraight holes 33 open onto a connector housing concave portion 34 thatis provided in a top surface 30 a of the connector housing 30. Theprotruding portions 31 have bridge portions 35 between adjacent taperedholes 32 and 32.

As is shown in FIG. 2, a number of connectors 37 that are supported on aconnector holder 36 are housed in the connector housing concave portion34 of the connector housing 30. The connectors 37 are provided atpositions corresponding to the respective straight holes 33, and areconnected to a voltage measuring circuit substrate (not shown). When theconnector unit 10 is correctly installed, the distal end portions 3 b ofthe terminals 3 in each separator 2 are connected to each of theconnectors 37.

The cover 40 is installed above the connector housing 30 and covers theconnector housing concave portion 34. The planar configuration andplanar dimensions thereof are the same as those of the connector housing30.

Next, the procedure for attaching the connector unit 10 to the stackhousing will be described. Note that, in the present embodiment, theconnectors 37 are fixed in advance in the connector housing concaveportion 34 of the connector housing 30.

Firstly, the terminals 3 of each separator 2 are inserted into therespective through holes 13 of the packing casing 11. In addition, thepacking casing 11 is fixed by screws to the stack housing (not shown).When the packing casing 11 is fixed to the stack housing, each of theterminals 3 that has been inserted through the through holes 13 is in astate of protruding upwards inside the packing housing concave portions12 of the packing casing 11.

Next, the packings 20 are placed inside the packing housing concaveportions 12 while the respective terminals 3 are inserted in the throughholes 21 in the packings 20. Here, because the horizontal cross sectionsof the through holes 21 in the packings 20 are slightly smaller than thehorizontal cross sections of the terminals 3, the internal surfaces ofthe bottom portion through holes 21 a are in tight contact with theexternal surfaces of the base portions 3 a of the terminals 3, and theinternal surfaces of the top portion through holes 21 b are in tightcontact with the external surfaces of the distal end portions 3 b of theterminals 3. FIGS. 6 and 7 show states when the placing of the packings20 inside the packing housing concave portions 12 has been completed. Atthis time, the bottom surfaces 12 a of the packing housing concaveportions 12 are in contact with the lip seal portions 24 of the packings20 so as to support the packings 20 from beneath, and the inner sidesurfaces of the packing housing concave portions 12 envelop the sidesurface 27 of the packings 20. In addition, the apex portions 25 a ofthe packings 20 are positioned slightly lower than the top surface 11 aof the packing casing 11, and the distal end portions 3 b of therespective terminals 3 that penetrate the respective through holes 21are in a state of protruding upwards beyond the top surface 11 a of thepacking casing 11. Accordingly, in the terminals 3, the base portions 3a that are covered by resin remain inside the through holes 21 in thepackings 20, and only the distal end portions 3 b whose metal surfacesare exposed are exposed from the packings 20.

Next, the protruding portions 31 and 31 of the connector housing 30 areinserted into the packing housing concave portions 12 and 12 of thepacking casing 11 while the respective terminals 3 that protrude fromthe packings 20 are being inserted into the tapered holes 32 and thestraight holes 33 of the connector housing 30. The tapered holes 32 ofthe protruding portions 31 cover the protruding portions 25 of thepackings 20. Note that because the internal surfaces 32 a of the taperedholes 32 are configured so as to match the side surfaces 25 b of theprotruding portions 25, the internal surfaces 32 a of the tapered holes32 are in surface contact substantially uniformly with the side surfaces25 b of the protruding portions 25. Note also that the height of theprotruding portions 31 is set in advance such that, in a state in whichthe tapered holes 32 cover the protruding portions 25, a gap of apredetermined size is created between the bottom surface 30 b of theconnector housing 30 and the top surface 11 a of the packing casing 11.

Moreover, in a state in which the tapered holes 32 cover the protrudingportions 25, the respective terminals 3 that penetrate the straightholes 33 are in a state of protruding upwards inside the connectorhousing concave portions 34, and each of the connectors 37 is connectedto a distal end portion 3 b of the terminals 3.

Next, the cover 40 is placed on the connector housing 30 and, togetherwith the connector housing 30 and the packing casing 11, it is fastenedto the stack housing by bolts (not shown). As a result, the protrudingportions 31 of the connector housing 30 press the packings 20 so thatthe packings 20 are compressed, and, as is shown in FIGS. 8 and 9, thebottom surface 30 b of the connector housing 30 is placed in contactwith the top surface 11 a of the packing casing 11. FIGS. 8 and 9 showstates in which this fastening is completed, however, the connectors 37and the cover 40 have been omitted from these drawings.

In a fastened state, the lip seal portions 24 of the packings 20 arecompressed, and are substantially flush with the bottom surfaces 22. Thelip seal portions 24 are placed in firm pressure contact with the bottomsurfaces 12 a of the packing housing concave portions 12 of the packingcasing 11. Because of this, it is possible to reliably seal the areasurrounding the through holes 13, and it is possible to reliably preventmoisture from the outside from encroaching into the stack housing viathe gaps between the internal surfaces of the packing housing concaveportions 12 and the external surfaces of the packings 20.

In a fastened state when the lip seal portions 24 are compressed,because the bottom surfaces 22 of the packings 20 are supported by thebottom surfaces 12 a and the bridge portions 14 of the packing housingconcave portions 12, and because the packings 20 are compressed whilethe inner surfaces 32 a of the tapered holes 32 in the connector housing30 are in surface contact with the four side surfaces 25 b of theprotruding portions 25 of the packings 20, the protruding portions 25 ofthe packings 20 are compressed by a force exerted obliquely inwards atall of the four side surfaces 25 b. As a result, because the internalsurfaces of the through holes 21 in the packings 20 are in tighterpress-contact with the external surfaces of the terminals 3, theperipheries of the through holes 21 can be reliably sealed, and it ispossible to reliably prevent moisture from the outside from encroachinginto the stack housing via the gaps between the through holes 21 in thepackings 20 and the terminals 3.

In addition, because the side surfaces 25 b of the protruding portions25 of the packings 20 are slanted, the contact area (namely, the area ofthe seal portion) between the side surfaces 25 b and the internalsurfaces 32 a of the tapered holes 32 can be increased, and theperformance of the seal in the tapered holes 32 can be increased.Accordingly, it is possible to reliably prevent moisture from theoutside from encroaching into the stack housing via the gaps between thetapered holes 32 in the connector housing 30 and the protruding portions25 of the packings 20.

In this manner, according to the fuel cell stack 1 of the presentembodiment, because it is possible to reliably seal the areas betweenthe packing housing concave portion 12 of the packing casing 11 and thepacking 20, and between the through holes 21 in the packing 20 and theterminals 3, and between the tapered holes 32 in the connector housing30 and the packing 20, it is possible to reliably prevent moisture fromencroaching from the outside into the stack housing, and it is possibleto prevent short-circuiting inside the stack housing such asshort-circuiting between cells.

Moreover, because it is possible to group together the plurality ofterminals 3 that constitute the terminal group 3A and to seal them usinga single packing 20, the waterproof structure of the connector unit 10can be simplified. Furthermore, because the positioning of the terminals3 can be performed simply and accurately, the connections between theterminals 3 and the connectors 37 can be made easily.

FURTHER EXAMPLES

Note that the present invention is not limited to the above describedembodiment.

For example, as is shown in FIG. 10, it is possible to form the sidesurfaces 25 b of the protruding portions 25 of the packings 20 with theleft and right end portions joined by curved surfaces such that a ridgeline is not created. The tapered holes 32 in the connector housing 30are also formed with the same configuration. If this type of structureis employed, then because there is no ridge line on the side surfaces 25b of the protruding portions 25 of the packings 20, the followingness ofthe packings 20 to the inner surfaces 32 a of the tapered holes 32 whenthe packings 20 are deformed by being compressed is excellent, and theadhesion of the packings 20 to the tapered holes 32 is increased. As aresult, the sealing properties can be further improved.

Moreover, in the above described embodiment, terminals 3 are providedfor all the separators 2, however, it is also possible for the terminals3 to be provided for just a portion of the separators 2.

A further embodiment of the fuel cell stack of the present inventionwill now be described with reference made to FIGS. 11 through 20.

The exterior structure of the fuel cell stack of the present embodimentcan be made the same as that of the fuel cell stack 1 (see FIG. 1) ofthe above described embodiment.

As is shown in FIG. 11, the separators 52 are provided with plate-shapedterminals 53 that extend upwards from a top end portion of theseparators 52. In a state in which the separators 52 are stacked, theplacement positions of the terminals 53 are offset from each other inadjacent separators 52 and 52. As a result, two columns of terminalgroups 53A and 53A are formed in columns running in the stackingdirection. Base portions 53 a of these terminals 53 are coated inrubber, while metal surfaces of distal end portions 53 b thereof areexposed. The base portions 53 a are inserted through windows (not shown)in the stack housing, and the distal end portions 53 b protrude towardsthe connector unit 10.

The connector unit 10 is provided with a packing casing 61, two packings70 and 70, a connector housing 80, and a cover 90.

The packing casing 61 is a member that is installed on a top portion ofthe stack housing. Packing housing concave portions 62 that are formedin a narrow, elongated shape running in the stacking direction of theseparators 52 are provided in a relationship of 1 to 1 with eachterminal group 53A on a top surface 61 a of the packing casing 61 inpositions corresponding to the terminal groups 53A and 53A. O-ringhousing grooves 65 that encircle the circumference of each packinghousing concave portion 62 are provided in a top surface 61 a of thepacking casing 61 (see FIG. 13), and an O-ring 66 is housed in eachO-ring housing groove 65.

As is shown in FIGS. 13 and 14, through holes 63 that penetrate thepacking housing concave portions 62 from a bottom surface 61 b areprovided in a relationship of 1 to 1 with each terminal 53 at positionsthat correspond to the respective terminals 53 in the bottom surface 61b of the packing casing 61. A bridge portion 64 is provided betweenadjacent through holes 63 and 63 in the same terminal group 53A. Topsurfaces of the bridge portions 64 are flush with a bottom surface 62 aof the packing housing concave portions 62. The through holes 63 areformed at a size that enables a gap to be left when the terminals 53 areinserted therein, and the bottom side of the through holes 63 is formedas a tapered hole while the top side thereof is formed as a straighthole.

The packings 70 and 70 are formed from an elastic material, and they arecontained respectively in the packing housing concave portions 62 of thepacking casings 61. Examples of the elastic material used to form thepackings 70 include nitrile rubber (NBR), hydrogenated nitrile rubber(HNBR), fluoro rubber (FKM, FFKM), acrylic rubber (ACM), silicone rubber(VMQ, FVMQ), urethane rubber (AU, EU), ethylene propylene rubber (EPM,EPDM), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM),epichlorohydrin rubber (CO, ECO), isoprene rubber (IR), styrenebutadiene rubber (SBR), butadiene rubber (BR), novornene rubber (NOR),natural rubber, and other thermoplastic elastomers.

As is shown in FIGS. 12 to 14, the packings 70 are composed ofsubstantially rectangular parallelepiped shaped base portions 77 and anumber of protrusions (i.e., circumferential wall portions) 78 thatprotrude upwards from the base portions 77. The protrusions 78 areprovided in a 1 to 1 relationship with the terminals 53.

The planar configuration and planar dimensions of the base portions 77are set such that they can be contained in the packing housing concaveportions 62 with substantially no gap between the two.

The protrusions 78 are formed in substantially rectangularparallelepiped shapes having four side surfaces 78 a, and top surfacesof the protrusions 78 are formed as truncated pyramid shaped protrudingportions 75. More specifically, the protruding portions 75 are formed asquadrangular pyramid base shapes (namely, quadrangular pyramids with thetop portion removed) that are made up of a flat apex portion 75 a andfour tapered surfaces (i.e., side surfaces) 75 b that are connected tothe flat apex portion 75 a and gradually widen towards the ends thereof.Each tapered surface 75 b is continuous from a side surface 78 a of theprotrusions 78.

Through holes 71 through which the terminals 53 are inserted are formedin the packings 70 in a relationship of 1 to 1 with the terminals 53 soas to extend from a bottom surface 72 to the apex portion 75 a of eachprotrusion 78. Namely, a protrusion 78 is provided independently foreach through hole 71.

A bottom side portion of each through hole 71 is formed as a bottomportion through hole 71 a through which the base portion 53 a, which iscovered by rubber, of the terminal 53 is inserted. The top side portionof each through hole 71 is formed as a top portion through hole 71 bthrough which the distal end portion 53 b, which has exposed metalsurfaces, of the terminal 53 is inserted. The top portion through hole71 b opens onto a center of the apex portion 75 a. The boundary betweeneach bottom portion through hole 71 a and top portion through hole 71 bis positioned below the protruding portion 75 of each protrusion 78 andabove the base portion 77. A horizontal cross section of the top portionthrough hole 71 b is set so as to be smaller than that of the bottomportion through hole 71 a. Moreover, a horizontal cross section of thebottom portion through hole 71 a is set so as to be slightly smallerthan the horizontal cross section of the base portion 53 a of a terminal53. In addition, the horizontal cross section of the top portion throughhole 71 b is set so as to be slightly smaller than the horizontal crosssection of the distal end portion 53 b of a terminal 53. A bottom edgeportion of the bottom portion through hole 71 a is formed as a taperedhole 71 c that widens as it moves down.

Note that when the packings 70 are contained inside the packing housingconcave portions 62, the packing housing concave portion 62 envelopsside surfaces of the packing 70, namely, the side surfaces 77 a of thebase portion 77 and the side surfaces 78 a of each protrusion 78 andsupports the bottom surface 72 of the packing 70.

The connector housing 80 is placed on top of the packing casing 61, andapplies pressing force to the packings 70 so as to compress the packings70. The planar configuration and planar dimensions of the connectorhousing 80 are the same as those of the packing casing 61. As is shownin FIG. 11, a connector housing concave portion 84 is formed in a topsurface 80 a of the connector housing 80.

As is shown in FIGS. 13 and 14, narrow elongated protruding portions 81and 81 are provided in parallel with each other at positionscorresponding to the respective terminal groups 53A and 53A on thebottom surface 80 b of the connector housing 80. The planarconfiguration and planar dimensions of each protruding portion 81 areset such that they can be inserted in the packing housing concaveportions 62 of the packing casing 61 so that a small gap is left.

Through holes 83 that penetrate the connector housing concave portion 84from the bottom surface 81 a thereof are provided in a relationship of 1to 1 with the terminals 53 at positions corresponding to the respectiveterminals 53. Adjacent through holes 83 are separated by bridge portions85. Top portions of the through holes 83 that open onto the connectorhousing concave portion 84 form straight terminal insertion holes 86through which the distal end portions 53 b of the terminals 53 areinserted with a gap between themselves and the insertion holes 86.Bottom portions of the through holes 83 form packing containing holes 87that house the protrusions 78 of the packings 70.

Internal surfaces of the top portions of the packing containing holes 87that are continuous from the terminal insertion holes 86 form taperedsurfaces 87 a whose cross section becomes gradually narrower as itapproaches the terminal insertion hole 86. The tapered surfaces 87 aform a shape that conforms to the tapered surfaces 75 b of theprotruding portions 75 of the packings 70. The tapered surfaces 87 afunction as pressing surfaces that press the tapered surfaces 75 b. Incontrast, bulges 87 b that bulge inwards and have a semicircular crosssection are formed on bottom end internal surfaces of the packingcontaining holes 87. The internal dimension of the packing containingholes 87 at the maximum bulge point of the bulges 87 b is slightlysmaller than the external dimensions of the side surfaces 78 a of theprotrusions 78 of the packings 70, so that the bulges 87 b function aspressing surfaces that press the side surfaces 78 a of the protrusions78. In addition, the bottom ends of the tapered surfaces 87 a and thetop ends of the bulges 87 b are connected by flat surfaces 87 c that areflat in the vertical direction.

As is shown in FIG. 11, a number of connectors 89 that are supported ona connector holder 88 are housed in the connector housing concaveportion 84 of the connector housing 80. The connectors 89 are providedat positions corresponding to the respective terminal insertion holes86, and are connected to a voltage measuring circuit substrate (notshown). When the connector unit 10 is correctly installed, the distalend portions 53 b of the terminals 53 in each separator 52 are connectedto each of the connectors 89.

The cover 90 is installed above the connector housing 80 and covers theconnector housing concave portion 84. The planar configuration andplanar dimensions thereof are the same as those of the connector housing80.

Next, the procedure for attaching the connector unit 10 to the stackhousing will be described. Note that, in the present embodiment, theconnectors 89 are fixed in advance in the connector housing concaveportion 84 of the connector housing 80.

Firstly, the terminals 53 of each separator 52 are inserted into therespective through holes 63 of the packing casing 61. In addition, thepacking casing 61 is fixed by screws to the stack housing (not shown).When the packing casing 61 is fixed to the stack housing, each of theterminals 53 that has been inserted through the through holes 63 is in astate of protruding upwards inside the packing housing concave portions62 of the packing casing 61. Next, the O-rings 66 are placed in therespective O-ring housing groove 65 in the packing casing 61. Note thatthe cross-sectional dimensions of the O-ring hosing grooves 65 and theO-rings 66 are set such that top end portions of the O-rings 66 protrudeslightly from the top surface 61 a of the packing casing 61.

Next, the packings 70 are placed inside the packing housing concaveportions 62 while the respective terminals 53 are inserted in thethrough holes 71 in the packings 70. Here, because the horizontal crosssections of the through holes 71 in the packings 70 are slightly smallerthan the horizontal cross sections of the terminals 53, the internalsurfaces of the bottom portion through holes 71 a are in tight contactwith the external surfaces of the base portions 53 a of the terminals53, and the internal surfaces of the top portion through holes 71 b arein tight contact with the external surfaces of the distal end portions53 b of the terminals 53. FIGS. 13 and 14 show states when the placingof the packings 70 inside the packing housing concave portions 62 hasbeen completed. At this time, the bottom surfaces 62 a of the packinghousing concave portions 62 are in contact with the bottom surfaces 72of the packings 70 so as to support the packings 70 from beneath, andthe inner side surfaces of the packing housing concave portions 62envelop the packings 70. In addition, the apex portions 75 a of thepackings 70 are positioned at substantially the same height as the topsurface 61 a of the packing casing 61, and the distal end portions 53 bof the respective terminals 53 that penetrate the respective throughholes 71 are in a state of protruding upwards beyond the top surface 61a of the packing casing 61. Accordingly, in the terminals 53, the baseportions 53 a that are covered by rubber remain inside the through holes71 in the packings 70, and only the distal end portions 53 b whose metalsurfaces are exposed are exposed from the packings 70.

Next, the protruding portions 81 and 81 of the connector housing 80 areinserted into the packing housing concave portions 62 and 62 of thepacking casing 61 while the respective terminals 53 that protrude fromthe packings 70 are being inserted into the respective through holes 83of the connector housing 80, and the respective protrusions 78 of thepacking 70 are inserted into the respective packing containing holes 87in the protruding portions 81. At this time, the bulges 87 b in thepacking containing holes 87 are moved downwards while they press againstthe side surfaces 78 a of the protrusions 78 of the packings 70 so as tocompress these side surfaces 78 a. Moreover, the tapered surface 87 a ofthe respective packing containing holes 87 cover the tapered surfaces 75b of the respective protruding portions 75 of the packings 70, and thebottom surface 80 b of the connector housing 80 is placed on top of theO-rings 66. Because the tapered surfaces 87 a of the packing containingholes 87 have a configuration that conforms to the tapered surfaces 75 bof the packings 70, the tapered surfaces 87 a are in surface contactsubstantially uniformly with the tapered surfaces 75 b. In this state,the bottom surface 80 b of the connector housing 80 is positionedslightly away from the top surface 61 a of the packing casing 61.Moreover, the distal end portions 53 b of the respective terminals 53that penetrate the through holes 83 are in a state of protruding upwardsinside the connector housing concave portions 84, and each of theconnectors 89 is connected to the distal end portion 53 b of theterminals 53.

Next, the cover 90 is placed on the connector housing 80 and, togetherwith the connector housing 80 and the packing casing 61, it is fastenedto the stack housing by bolts (not shown). FIGS. 15 and 16 show statesin which this fastening is completed, however, the connectors 89 and thecover 90 have been omitted from these drawings.

As a result of this fastening, the O-rings 66 are pressed by the bottomsurface 80 b of the connector housing 80 so that the O-rings 66 arecompressed, and the bottom surface 80 b of the connector housing 80 isplaced in contact with the top surface 61 a of the packing casing 61. Asa result, the O-rings 66 are in press contact with the bottom surface 80b of the connector housing 80 and the inner surface of the O-ringhousing groove 65 of the packing casing 61. It is thus possible toreliably seal the gaps between the packing casing 61 and the connectorhousing 80, and it is possible to reliably prevent moisture fromencroaching from the outside through these gaps into the packing housingconcave portions 62.

The tapered surfaces 75 b of the respective protruding portions 75 ofthe packings 70 are pressed and compressed by the tapered surfaces 87 aof the respective packing containing holes 87 in the connector housing80 so that both tapered surfaces 75 b and 87 a are in press contact witheach other around each through hole 71 in the packings 70. In additionto this, the bulge portions 87 b of the packing containing holes 87press and compress the side surfaces 78 a of the protrusions 78 on thepackings 70 along the entire circumference thereof. As a result, it ispossible to reliably prevent moisture from the outside from passingthrough the through holes 83 in the connector housing 80, and thenpassing between the internal surfaces of the packing containing holes 87and the external surfaces of the packings 70 and encroaching into thepacking collecting concave portions 62.

In addition, because the tapered surfaces 75 b of the protrudingportions 75 of the packings 70 are slanted, the contact area (namely,the area of the seal portion) between the tapered surfaces 75 b and thetapered surfaces 87 a of the packing containing holes 87 can beincreased, and the performance of the seal between the two taperedsurfaces 75 b and 87 a can be increased.

Furthermore, because the bottom surfaces 72 of the packings 70 aresupported by the bottom surfaces 62 a and the bridge portions 64 of thepacking housing concave portions 62, and because the packings 70 arecompressed while the tapered surfaces 87 a of the packing housingconcave portions 87 are in surface contact with the tapered surfaces 75b of the protruding portions 75 of the packings 70, the protrudingportions 75 of the packings 70 are compressed by a force exertedobliquely inwards at all of the tapered surfaces 75 b. Moreover, inaddition to this, the bulge portions 87 b of the packing containingholes 87 press and compress the side surfaces 78 a of the protrusions 78on the packings 70 along the entire circumference thereof. As a result,because the internal surfaces of the through holes 71 in the packings 70are in tighter press-contact with the external surfaces of the terminals53, the peripheries of the through holes 71 can be reliably sealed, andit is possible to reliably prevent moisture from the outside fromencroaching into the stack housing via the gaps between the throughholes 71 in the packings 70 and the terminals 53.

In addition, because the bottom surfaces 72 of the packings 70 are intight press contact with the bottom surface 62 a of the packing housingconcave portions 62 of the packing casing 61 and with the top surface ofthe bridge portions 64, it is possible to reliably seal any gaps betweenthe packing casing 61 and the packing 70, and it is possible to reliablyprevent moisture from passing through these gaps and encroaching intothe stack housing from the packing housing concave portions 62.

In this manner, according to the fuel cell stack 1 of the presentembodiment, because it is possible to reliably seal the areas betweenthe packing casing 61 and the connector housing 80, and between thepacking casing 61 and the packings 70, and between the through holes 71in the packings 70 and the terminals 53, and between the connectorhousing 80 and the packings 70, it is possible to reliably preventmoisture from encroaching from the outside into the stack housing, andit is possible to prevent short-circuiting inside the stack housing suchas short-circuiting between cells.

Moreover, because it is possible to group together the plurality ofterminals 53 that constitute the terminal group 53A and to seal themusing a single packing 70, the waterproof structure of the connectorunit 10 can be simplified.

Furthermore, because the positioning of the terminals 53 can beperformed simply and accurately, the connections between the terminals53 and the connectors 89 can be made easily.

Note that, as is shown in FIGS. 17 to 20, instead of providing the bulgeportions 87 b in the packing housing concave portions 87 of theconnector housing 80, the same operation and effects as in the abovedescribed embodiments can be obtained even if a structure is employed inwhich the bulge portions 79 that bulge outwards at the side surfaces 78a on the protrusions 78 of the packings 70 are provided so as toencircle the side surfaces 78 a, and when the protrusions 78 on thepacking 70 are inserted into the packing containing holes 87, the bulgeportions 79 of the packings 70 are pressed and compressed by the flatsurfaces 87 c of the packing containing holes 87. Note that, in thiscase, the flat surface 87 c of the packing containing holes 87 in theconnector housing 80 form the pressing surface.

FURTHER EXAMPLES

Note that the present invention is not limited to the above describedembodiment.

For example, it is possible to form the tapered surfaces 75 b of theprotruding portions 75 of the packings 70 so that they are joined bycurved surfaces such that a ridge line is not created in thecircumferential direction, and to form the side surfaces 78 a of theprotrusions 78 so that they are joined by a curved surface such that aridge line is not created in the circumferential direction, and to formthe packing containing holes 87 in the connector housing 80 with thesame configuration. If this type of structure is employed, then becausethe protrusions 78 (i.e., the circumferential wall portions) on thepackings 70 have a shape without a ridge line, the followingness of thepackings 70 to the packing containing holes 87 when the packings 70 aredeformed by being compressed is excellent, and the adhesion of thepackings 70 to the packing containing holes 87 can be increased. As aresult, the sealing performance can be further improved.

Moreover, in the above described embodiment, terminals 53 are providedfor all the separators 52, however, it is also possible for theterminals 53 to be provided for just a portion of the separators 52.

According to the first embodiment of the present invention, the sealingperformance between the through holes in the packing and the terminalsis improved. Moreover, because the terminals can be positioned andplaced in rows accurately, the terminals can be easily connected to theconnectors of the connector member.

Moreover, according to another embodiment of the present invention,because it is possible to increase the contact area (namely, the area ofthe seal portion) between the protruding portions on the packings andthe pressing surface of the connector members, and because it ispossible to place the internal surfaces of the through holes in thepackings in tighter press contact with the external surfaces of theterminals, the sealing performance is further improved.

According to another embodiment of the present invention, when thepackings are compressed and deformed, the followingness of theprotruding portions of the packings relative to the pressing surface isexcellent, and it is possible to improve the adhesion to the pressingsurface and further improve the sealing performance.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as limited by theforegoing description and is only limited by the scope of the appendedclaims.

1. A fuel cell stack that is provided with a plurality of stackedseparators, comprising: terminals that extend from at least one of anyseparators; packing formed from an elastic material for preventingmoisture from outside from encroaching into a stack housing, in whichare formed a plurality of through holes through which the terminals areinserted, and that has an independent circumferential wall portion foreach through hole; a packing casing that has a packing housing concaveportion that envelops the packing and supports a bottom surface of thepacking, and has through holes through which the terminals are inserted;and a connector member comprising a plurality of pressing surfaces,which correspond to the plurality of through holes formed in thepacking, and which press a top surface and side surfaces of therespective circumferential wall portions of the packing, wherein bulgeportions are provided on at least one of the side surfaces of thecircumferential wall portions and the pressing surfaces that press theside surfaces, wherein each bulge portion protrudes to press against theother of the side surfaces of the circumferential wall portions and thepressing surface, and internal surfaces of the through holes in thepacking are in contact without a gap with external surfaces of theterminals.
 2. The fuel cell stack according to claim 1, wherein thecircumferential wall portions of the packing have no ridge line in acircumferential direction thereof.
 3. The fuel cell stack according toclaim 1, wherein each of the through holes in the packing comprises abottom portion through hole at a lower side of the circumferential wallportion of the packing and a top portion through hole at an upper sideof the circumferential wall portion, and wherein the bulged portions areprovided on the pressing surfaces of the connector member such that anupper portion of the pressing surfaces presses the upper side of thecircumferential wall portion and the bulged portions press the lowerside of the circumferential wall portion.
 4. The fuel cell stackaccording to claim 1, wherein the packing casing comprises an O-ringthat encircles the packing housing concave portion.